Phospho-sulfurized phosphite esters and hydrocarbon compositions containing the same



3,459,662 PHOSPHO-SULFURIZED PHOSPHITE ESTERS AND HYDROCARBONCOMPOSITIONS CONTAINING THE SAME Shih-En Hu, Roselle, NJ., assignor toEsso Research and Engineering Company, a corporation of Delaware NoDrawing. Filed Jan. 31, 1967, Ser. No. 612,794 Int. Cl. (310m 5/24,7/46; C07f 9/04 U.S. Cl. 25246.7 11 Claims ABSTRACT OF THE DISCLOSUREReaction products of organic phosphite esters (mono-, di-, or tri-) witha phosphorus polysulfide are sludge inhibitors and anti-wear agents inlubricating oils or in middle distillate hydrocarbon fuels or residualhydrocarbon fuels, When used in amounts up to wt. percent based on theweight of the compounded compositions.

The present invention relates to the production of phosphite esterreaction products with phosphorus polysulfides, which products are foundto be particularly useful as additives when employed, in minor amounts,in hydrocarbon lubricating oils, in middle distillate hydrocarbon fuels,or in residual hydrocarbon fuels. Such reaction products have been foundto be particularly useful as additives in these hydrocarbon compositionsin order to inhibit oxidation, rust formation, sludge production, wear,and for dispersing any sludge which is formed and to the extent it isformed; thus preventing its deposit on the surfaces of automotiveengines, fuel pumps, and the like where it would cause fouling andplugging difliculties.

Various phosphite derivatives have, in the past, been produced and usedas additives in both hydrocarbon fuel compositions and in lubricatingoil compositions for the purpose of inhibiting the corrosion ofbearings, minimizing bearing wear, and for the purpose of otherwiseprotecting the internal metal surfaces of pumps and automotive engines.This is accomplished by imparting load carrying ability to thelubricating oils, limiting the corrosion of hearings in engines andpumps, and improving the Wear qualities of the bearings and pumps and ininternal combustion engines. The problem of rust is minimized in fuelpumps handling residual or middle distillate hydrocarbon fractions andfuels. Many of these phosphite compounds have exhibited one or more ofthe aforementioned characteristics but few, if any, have been found tosatisfactorily cope with all or a majority of these problems from acommercial standpoint. High operating temperatures in internalcombustion engines tend to assert accelerated detrimental oxidativeinfluences on lubricating oils and this, of course, tends to result inthe premature breakdown of these oils with the resultant formation ofacids and other sludge-type materials which generally gum up, clog, andcorrode bearings and internal surfaces leading to excessive wear ofbearing surfaces and plugging difficulties in oil circulation systemsbecause of the excessive quantities of sludge formed. It is recognizedthat sludge formation, whether or not the sludge is deposited, is an anundesirable phenomenon associated with the use of lubricating oils andis to be minimized or avoided altogether if it is possible to do so.

The hereinafter, more fully described novel phosphite additives areashless in nature which means that they tend to eliminate the formationof deposits in combustion chambers and in the crankcases of internalcombustion engines where metal-containing sludge dispersants would, infact, leave a residue or ash-forming deposits under like circumstances.Many of the heretofore prepared metallic dispersants have certaindisadvantages. Some of atom 3,459,662 Patented Aug. 5, 1969 them are,for example, too corrosive to be used in lubricants or, because theyhave been neutralized with calcium carbonate or sodium hydroxide, theycontain metallic constituents Which form ash. They may also be toocorrosive, for practical purposes, toward copper-lead bearings orsilver-cadmium bearings. They may not, in themselves, exhibitantioxidant properties and antiwear properties in the oils containingthem thus making it necessary to add other compounds to take care ofthese problems arising by reason of the high temperature operation ofinternal combustion engines. The novel phospho-sulfurized phosphiteproducts hereinafter described accomplish the desired ends to a greaterextent than has heretofore been thought to be possible or attainable.

The novel phospho-sulfurized phosphite esters which serve as additivesfor middle distillate fuels, residual hydrocarbon fuels and as additivesin lubricating oils are pre pared by reacting a mono-, di-, ortriorganic phosphite ester with a polysulfide of phosphorus in liquidphase and at elevated or superatmospheric temperatures for a sufficientlength of time to introduce a polysulfide of phosphorus into thephosphite ester. The reactant organic phosphite ester may be representedby the formula:

wherein: R is a hydrocarbon radical selected from the group consistingof alkyl, chloralkyl, aryl, chloraryl, alkaryl, chloralkaryl, cycloalkyl, chlorcyclo alkyl, alkenyl, chloralkenyl, aralkyl, andchloraralkyl; and R and R are hydrogen or the same as R Thesephospho-sulfurized esters have been found to exhibit outstandingantioxidant, antiwear and sludge inhibiting properties when employed inlubricating oils for internal combustion engines or in fuels. They aresoluble in the above-mentioned hydrocarbon fuels and lubricating oils atleast to the extent of about 10 wt. percent which is generally the upperlimit of an amount suitable for use in either type of hydrocarbonmixture, i.e., lubricating oil or fuel. Further quantities or higherdegrees of solubility are unnecessary because the additives do notperform their functions to any greater degree or with any better resultsthan through the use of 10% or less of the additives. These noveladditives are excellent in inhibiting the formation of sludge, inminimizing bearing weight loss and they exhibit outstanding qualities inbeing able to disperse and maintain in dispersion any small amounts ofsludge that does form during the use of lubricating oils containingthese novel sulfurized phosphite ester reaction product additives.

The phosphite esters employed as reactants may be either the monoester,the diester, or the triester of phosphorous acid or mixtures of two ormore of these esters. Many of the esters employed in making usefuladditives, particularly those containing the smaller number of carbonatoms per molecule, are readily available commercially and their methodsof preparation are conventional. Some of the esters, particularly thosehaving the longer alkyl chains or hydrocarbon radicals or chlorinatedhydrocarbon radicals of the higher number of carbon atoms per radical,although presently not available commercially, are readily prepared bythe reacting of one, two, or three moles of the corresponding alcoholwith one mole of phosphorous trihalide such as phosphorous trichlorideor phosphorous tribromide. This is a conventional reaction and whilethere are other ways, also conventional, of producing these variousphosphite esters, the present invention is not concerned with theparticular method by which the phosphite esters are produced. In thosecases where monoor di-esters are formed, it is sometimes desirable,following the esterification reaction,

to treat the reacted mixture with Water, dilute aqueous caustic, ordilute aqueous mineral acid in order to hydrolyze off the residualchlorine or bromine atoms present by reason of the trivalent phosphorouscompound employed as the original reactant. Once this is accomplished,the mono-, di-, or tri-organic phosphite ester, or mixtures of two ormore of these, may be readily phosphosulfurized with a phosphorouspolysulfide but, surprisingly, it has been found that effectiveadditives are not produced if the phosphorus sulfide is present in andduring the phosphite esterification reaction. Only after the completionof the esterification reaction and the removal of reactant halogen is itpossible to treat with phosphorus polysulfide and secure an effectiveantioxidant, sludge inhibiting, antiwear agent.

Any of the phosphorus polysulfides conveniently available, i.e.,commercially marketed, may be employed. Representative of these specificcompounds are the following:

P S phosphorus sesquisulfide P S phosphorus disulfide RS -phosphorustrisulfide ES -phosphorus pentasulfide Specific phosphite esters whichare useful as reactants with the polysulfides of phosphorus areexemplified by the following specific phosphites. (A specific listing ofthe mono ester is intended to include like listing of the diester andtriester as well; thus, for example, methyl phosphite is intended toalso include dimethyl phosphite and trimethyl phosphite):

Methyl phosphite, ethyl phosphite, n-propyl phosphite, isopropylphosphite, butyl phosphite, pentyl phosphite, hexyl phosphite,cyclohexyl phosphite, heptyl phosphite, nonyl phosphite, decylphosphite, lauryl phosphite, lorol phosphite, cetyl phosphite, octadecylphosphite, heptadecyl phosphite, phenyl phosphite, alpha or beta napthylphosphite, alpha or beta naphthenyl phosphite, benzyl phosphite, tolylphosphite.

The mixed aryl phosphites, for example:

Methyl,phenyl phosphite; dimethyl,phenyl phosphite; amyl,phenylphosphite; diamyl,phenyl phosphite; nonylphenyl phosphite, nonyl,phenylphosphite; (4-amylphenyl) phosphite, 4-amylphenyl diethyl phosphite,dioctadecyl phenyl phosphite, octadecyl di-phenyl phosphite, isobutylphenyl phosphite, nonyltolyl phosphite, nonyl,ditolyl phosphite;polyisobutenyl diphenyl phosphite, dipolyisobutenyl phosphite,di-polyisobutenyl phenyl phosphite, (polyisobutenyl phenyl) phosphite,chlorethyl phosphite, chlorbutyl phosphite, chloroctyl phosphite,chlorphenyl phosphite, chlorbenzyl phosphite, chlorotolyl phosphite,(chloropolyisobutenyl diphenyl) phosphite, dipolyisobutenyl(chlorbenzyl) phosphite, di-polyisobutenyl (chlorpolyisobutenyl)phosphite.

The lorol radicals mentioned above in connection with the specificphosphites that may be employed are derived from the correspondingprimary alcohols obtained by the carboxylic reduction of cocoanut orpalm kernel oils. These crude mixtures contain a major amount of lorolalcohol together with minor amounts of octyldecyl and myristrylalcohols. A typical lorol mixture boils between about 140 C. and about190 C. at 50 mm. mercury pressure.

The interaction of the heretofore mentioned phosphite esters with aphosphorus polysulfide is carried out in liquid phase either in thepresence or absence of inert solvents such as normally liquidhydrocarbon petroleum solvents, for example, petroleum ether, hexane,chlorhexane, hexene, nonyl heptane, benzene, toluene, and the like. Thereaction is generally carried out in the absence of solvents and between1 and 3 moles of phosphite are employed per mole of phosphoruspolysulfide; the sultide being gradually and directly added to thephosphite, starting at ambient temperatures, for about 1 hour, afterwhich the temperature may be gradually increased up to between about 40C. and about 200 C., preferably between about 75 C. and C. The period ofreaction, i.e., of maintaining the reaction temperature, is generallybetween about 1 and about 10 hours, preferably, between about 2 hoursand about 6 hours, after which the reaction mixture is allowed to coolto ambient temperature and any unreacted sulfide is removed from thereacted mixture by filtration. If necessary, sufiicient superatmosphericpressure is applied in order to maintain the reaction mixture in liquidphase under the other reaction conditions obtaining. The amount ofsuperatmospheric pressure employed is not critical except thatsufficient pressure is maintained in order to insure a liquid phasereaction mixture.

Many of the phosphites above mentioned are available commercially. Forthose specifically enumerated above which are not availablecommercially, it is a simple matter to effect a reaction betweenphosphorous trichloride or tribromide and the corresponding monohydricalcohol in which the mole ratios of the alcohol to the phosphorouscompound are maintained between 1:1 and about 3:1 depending upon whetheror not it is desired to produce a mixture predominating in the mono-,di-, or tri-phosphite ester. Preferably a mole ratio of alcohol tophosphorous trihalide of between about 0.75 and about 3.5 to 1 ismaintained. Any solvents which are employed in effectuating the reactionare distilled off at atmospheric pressures or under slight vacuum, ifneed be.

One convenient method of producing an additive, although the followingspecific examples do not employ it, involves the use of lubricating oilfractions, middle distillate or residual fuel fractions as the reactionor solvent medium so that, upon a final filtration to remove any tracesof unreacted sulfide, an oil concentration suitable for direct additionto lubricating oils, middle distillate fuels or residual fuels may beaccomplished without further treatment. Usually theseoil-phospho-sulfurized phosphite ester concentrations will containbetween about 50% and about 75% by weight of phospho-sulfurizedphosphite ester and may be marketed as such and they may be used in manyinstances as the direct and only additive for the materials in whichthey are to be ultimately employed.

The novel phospho-sulfurized phosphite esters are useful in lubricatingoil compositions of the type employed in internal combustion engines ofeither the gasoline or diesel types as well as in heavy duty gas enginelubricants. The amounts incorporated into such lubricating oils rangebetween about 0.001 and about 10.0 wt. percent generally, preferablybetween about 0.01 and about 5.0 wt. percent. Additionally, the noveladditives herein described find usage in the middle distillate fuels andresidual fuels for the purpose of imparting anti-rust and anti-corrosiveproperties to the fuels. Such fuels are those normally sold commerciallyas gasoline, jet fuel, kerosene, heating oil fuel, and the heavyresidual fuel oils such as Bunker-C. When so used, the additives areincorporated into these fuels in amounts ranging between about 0.001 andabout 5.0 wt. percent, preferably between about 0.01 and about 1.5 wt.percent. All of the above percentage figures are based on the totalweight of the composition.

The fuels and lubricating oil compositions described above may alsoinclude conventional additives present in like or smaller amounts, forexample, they may contain oxidation inhibitors, such as phenyl alphanaphthylamine; rust inhibitors such as over-based alkaline earth metalpetroleum sulfonates and alkyl amines; detergent additives such asover-based calcium petroleum sulfonate, phospho-sulfurizedpolyisobutylene, barium phenate sulfide, or a so-called ashlessdispersant such as the polyisobutylene-substituted succinic anhydridereaction product with a polyethylene polyamine such as tetraethylenepentamine. Additionally, conventional additives particularly employed inlubricating oil compositions include viscosity index improvers such aslong chain wax alkylated naphthylene, the polymers of acrylates andmethacrylates esterified with long chain monohydric alcohols, and thecorresponding polymethacrylates.

Two typical specific lubricating motor oil bases have been employed.Both are of the SAE 10W-30 grade and they differ from one another onlyin a minor manner. In one case, the base oil is composed of 90.6% of asolvent extracted, dewaxed neutral oil from Mid-Continent paraffiniccrude. It has a viscosity of 105115 SUS (Saybolt Universal Seconds) at100 F. and a pour point of about F. The remaining 9.4% is the same typeof oil but is one having a viscosity of about 450500 SUS at 100 F. Thisoil base is employed in carrying out the Falex wear test. Anothersimilar oil that is suitable as an oil base is composed of 90.75% of thesame oil described before except that it has a viscosity of betweenabout 150 and about 175 SUS at 100 F., the remainder of the oil baseconstituting the same oil as is used in the previously described blendin the amount of 9.4%. Both oils contain approximately 10.6% of aviscosity index improver, namely, polyisobutylene, and about 3.78% of anashless dispersant identified as the polyisobutylene succinic anhydrideimide of tetraethylene pentamine. The oil base comprised about 83% ofthe total compounded oil compositions plus minor amounts, i.e., lessthan 1%, of overbase calcium petroleum sulfonate and wax-alkylatednaphthalene plus the copolymer of lorol fumarate with vinyl acetate.Where the novel antiwear and antioxidant additives are employed, theyare used in the amount of 1.22 wt. percent, based on the totalcompounded composition.

The Falex wear test was made by running the test compositions in a Falexwear test machine. This test was conducted for the purpose of measuringthe amount of wear which the bearings would encounter under extremelysevere conditions using the test oil compositions. A steel pin isrotated at 290 r.p.m. between two V blocks for 30 minutes at 500 lbs.per square inch direct gauge pressure. The entire assembly is immersedin the test oil composition at ambient temperature. The wear performanceof the test compounded oil is judged by the weight loss, in milligrams,of the steel pin. Pin seizure or borderline pin seizure conditions areavoided under the conditions, or, if they occur, the test oil is deemedto have failed in antiwear qualities.

A second test was carried out in order to evaluate the sludge-handlingability of the tested lubricating oil compositions in which thetemperature of the oil was cyclically raised and lowered over a periodor" many hours in order to determine the oxidation stability and thesludge inhibiting or sludge forming tendencies of the novel additives inthe oil compositions. A 6-cylinder Ford engine was used which employed astandard carburetor. It was operated at a standard speed of 1,500 r.p.m.plus or minus 15 r.p.m. under a constant load of 140 plus or minus 2foot lbs. of torque. The oil sump temperature was maintained in the coldphase at 150 F. :5 F. and at 215 F. 15 F. in the hot phase. The coldphase operation was for a period of 5 hours and alternated with a hotphase operation of 2 hours. This is known as the Ford cyclic temperaturesludge test.

Still another test was carried out known as a lubricant stability testwhich evaluates the compounded oils under accelerated oxidativeconditions. The method is designed primarily to evaluate the stabilityof railroad Diesel lubricants wherein the compounded oils are subjectedto elevated temperatures (342 F.) for a period of 23 hours in contactwith copper-lead alloy, and silver, bearing metals, i.e., thoseencountered in heavy duty Diesel engines. Air is bubbled through thetest oil while stirring it under these conditions and for the length oftime indicated. Air is bubbled in at about 2 cubic feet per hour and thestirrer is rotated at about 600 r.p.m. Fresh metal specimens areinserted into the oil every three hours. Saybolt viscosities at 100 F.are measured and the rating of the oil is computed on the basis ofpercent viscosity increase after 23 hours.

The invention will be more completely understood by reference to thefollowing examples but it is to be distinctly understood that it is notto be limited to these examples since they are only exemplary orrepresentative in nature. All percentages are with respect to weightpercent.

EXAMPLE 1 25 grams of phosphorus pentasulfide Was gradually added to 84grams of triethyl phosphite over a period of about 1 hour. The reactingmixture was stirred for an additional 3 hours without the addition ofexternally supplied heat; at the end of which time the reaction mixturewas clear and the reaction had stopped. The product analyzed 19.8 wt.percent of phosphorus and 16.3 wt. percent of sulfur.

EXAMPLE 2 About 279 grams of lorol alcohol was reacted with about 69grams of phosphorous trichloride by gradually adding the same to thephosphorous trichloride at a temperature of about 10 C. over a period oftwo hours. Stirring was continued at room temperature until no more gaswas evolved. The reaction was completed after about 20 hours. Thetriester had a phosphorus content of 4.46 wt. percent.

About 120 grams of the trilorol phosphite was gradually admixed withabout 20 grams of phosphorus pentasulfide at a temperature of about C.over a period of about 6 hours. The reacted mixture was filtered toremove all unreacted phosphorus pentasulfide. The final product analyzed6.04 Wt. percent phosphorus and 7.60 wt. percent sulfur.

EXAMPLE 3 An SAE 10W30 grade internal combustion engine lubricating oilwas prepared. It contained about 75 .29 wt. percent of a solventextracted, de-waxed, neutral oil from Mid-Continent paraffinic crudehaving a viscosity of SUS (Saybolt Universal Seconds) at 100 F. and apour point of about 0 F.; about 7.7 wt. percent of the same type of oilbut having a viscosity of about 450-500 SUS at 100 F.; about 10.5 wt.percent of a viscosity index improver (polyisobutylene); about 0.5 wt.percent of a pour point depressant (a wax alkylated naphthalene); about3.75 wt. percent of an ashless dispersant (the condensation product ofpolyisobutylene succinic anhydride with tetraethylene pentamine); andslightly less than 1% of an ash forming detergent, i.e., an over-basedcalcium alkaryl sulfonate. In addition, in each of the tests, the baseoil contained, as an additive, an antiwear agent in the amount of 1.22Wt. percent.

The compounded compositions were subjected to a standard Falex antiwearmachine test for 30 minutes using a bearing pressure of 500 lbs. persquare inch. The figures given in the following table show the weightloss of the steel pin, in milligrams.

TABLE Bearing weight loss, milligrams ABase oil-i-phospho-sulfurizedproduct of Example 1 3.3 B-Base oil+phospho-sulfurized product ofExample 2 3.6 CBase oiH-conventional antiwear additive 1 7.4

1 Zinc di-(C4-C5 alkyl) dithiophosphate.

It is apparent from a consideration of the above data that the bearingweight loss in the case of the use of phos phosulfurized phosphites asadditives is only 50% of that attained in the use of a conventionalantiwear additive and that automotive engine lubricating oils containingthe phospho-sulfurized phosphites possess high qualities from thestandpoint of antiwear properties.

7 EXAMPLE 4 It was found that the use of the cyclic temperature sludgingtests showed a definite inhibition of oxidation and a satisfactorydispersion of what little sludge was formed in the use of thesephospho-sulfurized phosphites as compared with the same base oil withoutthe phosphosulfurized phosphites. The base oil, in all tests, was thesame as that described in Example 3.

A further comparative series of lube oil oxidative stability tests wereundertaken following the procedure hereinbefore set forth in order todetermine the relative resistance to oxidation of the novel compoundedlubricating oil. Oil A, the base oil, contained no phospho-sulfurizedproduct but comprised about 90% of solvent dewaxed, neutralMid-Continent lube oil having a viscosity of about 150 SUS at 100 F. andabout 10% of polyisobutylene of l4,00015,000 viscosity average molecularweight (Staudinger). Oil B was the same as Oil A but contained, inaddition, about 1% of the phospho-sulfurized phosphite of Example 2.

Lube stability test Percent viscosity increase after 23 hours Oil A100.0 Oil B 8.3

Since this test measures the oxidative stability of the oil blends andthe less the increase in viscosity the better the oil, it is readilyapparent that the use of 1.0% of the product of Example 2 (Oil B) givesrise to a compounded oil of astonishing stability to oxidation.

Having now thus fully described and illustrated the nature of theinvention, what is desired to be secured by Letters Patent is:

1. A hydrocarbon composition comprising a major amount of a hydrocarbonliquid selected from the group consisting of lubricating oils, middledistillate fuels, and residual fuels and between about 0.001 and about10.0 wt. percent of the reaction product of organic phosphite estershaving the formula:

R20 wherein R is a radical selected from the group consisting of alkyl,chloralkyl, aryl, chloraryl, aralkyl, chloraralkyl, cycloalkyl,chlorcycloalkyl, alkaryl, chloralkaryl, and R and R are hydrogen or thesame as R with a polysulfide of phosphorus.

2. A hydrocarbon composition comprising a major amount of a hydrocarbonliquid selected from the group consisting of lubricating oils, middledistillate fuels, and residual fuels and between about 0.001 and about10.0

wt. percent of the reaction product as in claim 1 wherein the phosphiteester is a triester.

3. A hydrocarbon composition comprising a major amount of a hydrocarbonliquid selected from the group consisting of lubricating oils, middledistillate fuels, and residual fuels and between about 0.001 and about10.0 wt. percent of the reaction product as in claim 2 wherein thephosphite ester is a trialkyl phosphite ester.

4. A hydrocarbon composition comprising a major amount of hydrocarbonliquid selected from the group consisting of lubricating oils, middledistillate fuels, and residual fuels and between about 0.001 and about10.0 Wt. percent of the reaction product as in claim 3 wherein thetrialkyl phosphite ester is trilorol phosphite ester.

5. A hydrocarbon composition comprising a major amount of a hydrocarbonliquid selected from the group consisting of lubricating oils, middledistillate fuels, and residual fuels and between about 0.001 and about10.0 -wt. percent of the reaction product as in claim 3 wherein thetrialkyl phosphite ester is triethyl phosphite.

6. A hydrocarbon composition comprising a major amount of a hydrocarbonliquid selected from the group consisting of lubricating oils, middledistillate fuels, and residual fuels and between about 0.001 and about10.0 wt. percent of the reaction product as in claim 1 wherein thephosphorus polysulfide is phosphorus pentasulfide.

7. A hydrocarbon composition comprising a major amount of a hydrocarbonliquid selected from the group consisting of lubricating oils, middledistillate fuels, and residual fuels and between about 0.001 and about10.0 wt. percent of the reaction product as in claim 3 wherein thephosphorus polysulfide is phosphorus pentasulfide.

8. A hydrocarbon composition comprising a major amount of a hydrocarbonlubricating oil and between about 0.001 and about 10.0 wt. percent ofthe reaction product as in claim 4.

9. A hydrocarbon composition comprising a major amount of a hydrocarbonlubricating oil and between about 0.001 and about 10 wt. percent of thereaction product as in claim 5.

10. A hydrocarbon composition comprising a major amount of a hydrocarbonlubricating oil and between about 0.001 and about 10 Wt. percent of thereaction product as in claim 6.

11. A hydrocarbon composition comprising a major amount of a hydrocarbonlubricating oil and between about 0.001 and about 10 wt. percent of thereaction product as in claim 7.

References Cited UNITED STATES PATENTS 2,231,301 2/ 1941 Smith 25246.62,589,326 3/1952 Oberright 252-466 2,595,170 4/1952 Rudel et al. 25246.62,733,235 1/ 1956 Cross et al. 252--46.6 X

DANIEL E. WYMAN, Primary Examiner W. CANNON, Assistant Examiner US. Cl.X.R.

